I have just finished the 4 heroes fight in the Stonegarden, and suddenly my Sebille has wings. Permanently, as far as I can tell, I've moved around and waited for a while, as well as saved and reloaded. She is not wearing the vulture armor, though Beast is, in the same party (neither are the PC if that's relevant). As far as I can tell this is not intended, and I couldn't find anyone else having the same bug. I'm not exactly complaining, I love how wings look on her (in my past 2 playthroughs she had the vulture armor all game, they just look so good with her), but I am rather baffled. Included is a screenshot, and she can use the flight skill completely normally.